Question

The largest number of molecules is in

• A. $36g$ of $H_{2}O$
• B. $28g$ of $C{O}_2$
• C. $46g$ of ethyl alcohol
• D. $54g$ of nitrogen pentaoxide $(N_2{O}_5)$

Answer 1

Answer: (A)

Number of molecules present in $36g$ of water $=\frac{36}{18}\times N_A=2N_A$
Number of molecules present in $28g$ of $CO=\frac{28}{28}\times N_A=N_A$
Number of molecules present in $46g$ of $C_2{H}_{5}OH=\frac{46}{46}\times N_A=N_A$
Here, $N_A$ is Avogadro's number. Hence, $36g$ of water contain the largest $\left(2N_A\right)$ number of molecules.